1. Field of the Invention.
The present invention relates, in general, to the construction of sewage systems, and in particular, to the construction of storm drains. Specifically, the invention relates to the construction of a cover for a storm drain collection box.
2. Description of the Prior Art.
A sewage system is any of several drainage systems for carrying surface water and/or sewage for disposal. Each of the several drainage systems is generally subject to its own particular design considerations depending on the use made of that system. For example, a storm drain is a drain which conducts storm surface, or wash water, or drainage after a heavy rain from a building to a storm or a combined sewer; whereas a sanitary sewer which is restricted to carrying sewage and to which storm and surface waters are not admitted.
Any sewage system generally includes a collection box into which the fluid to be carried away flows, and an appropriate drainage conduit which is fluidically connected to the collection box. The collection box is generally a cast-in-place concrete structure which includes side walls, a rear wall, and a front wall, with the fluid entering a collection box throat which is located adjacent to the front wall. The casting of such structures generally includes the use of falsework, which is a temporary support used until the main structure is strong enough to support itself. This falsework generally includes wood panels and he like formed by carpenters on the site according to the general shape and size of the structure being constructed. The semiliquid or viscous concrete is then poured into the falsework and allowed to harden, after which the top of the collection box is formed to close the collection box in the appropriate manner. Thus, the entire collection box is generally formed in at least two pours of concrete a first pour for the collection box walls and a second pour for the cover.
The top of the collection box also is formed using falsework which, in the past, has also been constructed in place by carpenters building a wood frame. This cover-forming falsework is then dismantled once the concrete of the cover has hardened. Again, the dismantling is done by hand.
Due to the manner of constructing the collection box, the general size and dimensions thereof may be subject to variations from a standard. However, since the cover falsework has been constructed by hand after the collection box sides have been formed, this dimension variation has not been a problem since it has been accounted for by the carpenter building the cover-forming falsework.
However, while permitting the cover-forming falsework to be matched and customized to the remainder of the collection box, this hand construction technique has many drawbacks. Such hand construction techniques are time consuming and wasteful of manpower during both the construction stage as well as during the dismantling stage.
However, in addition to wasting both time and money, such hand construction techniques may not result in a falsework that is the most ideal for the particular application. That is, for example, in the case of a storm sewer which is used to handle water in great quantities and often at high flow rates, the fluid entrance throat should be designed to most efficiently handle such flow rates and flow volumes. This design may include surfaces which are curved in particular manners and which may be located with respect to each other at very specifically defined spacings to cause the fluid to flow into and through the throat in the most efficient manner. Such curves may not be efficiently produceable using the wood falsework construction techniques of the prior art. Accordingly, such falsework may produce a cover that is generally acceptable for use in storm drains, but is not the most efficient for such an application.
Still another problem with such hand construction techniques may result from a lack of quality control. Thus, for example, if many storm drains are being constructed, there may be variations among such drains that are actually constructed which may result in different drains accommodating different flow rates and different volumetric flows. This variation could result in one area of a single system flooding while other areas of that same system do not flood. Such variation may be detrimental to an overall construction site.
Yet another problem which might occur with such hand-construction techniques may be related to a lack of research and development feedback to the builders and from the builders to anyone conducting research which might be pertinent. Thus, for example, if there is any problem with flow patterns, these problems may not be solved properly when there is a hand construction due to a lack of communication between the people actually building the collection boxes and anyone who might be involved in a research and development project which might have some application to such flow patterns in systems of this type. This lack of communication may result in the people involved in the building of such systems failing to receive information on any new shapes or techniques being developed in various studies.
Such quality and research control and rapid construction of articles may be associated with factory production of prefabricated products. Prefabricated products are often, in general, expeditiously set up and dismantled. However, mass production and prefabrication techniques have not been applied to the production of sewer systems because they have many problems as applied to such systems.
For example, since, as above mentioned, each of the several different types of sewer systems is subject to its own individual considerations that may vary due to the exigencies of construction in a particular site, much of any particular sewer system is generally formed in place at the construction site and may vary in dimensions due to the vagaries of the terrain. Accordingly, a prefabricated falsework may not properly fit the rest of a collection box that has been formed on site and has its dimensions dictated by the terrain at that site. It is quite difficult, and may be impractical, to adequately account for such wide variations in a practical manner in a manufacturing process. For this reason, drainage system collection box construction has not, heretofore, used the techniques of prefabrication and mass production, and thus has not fully realized the advantages of prefabrication and ass production techniques, and still uses the techniques of on-site hand construction which have been used in this art for many years and which are subject to all of the above-discussed drawbacks.
Accordingly, there is need for a means and a method for applying the techniques of prefabrication and mass production to the art of constructing falsework for forming cast-in-place and precast collection boxes and covers, especially storm drain collection boxes and covers.